Calculate your spoke length ? Casio Programable calculator?

[Skyfarmer]

Just in case any one has an old Casio programable calculator...mine is an fx7700 graphics unit.

Any way, was bored the other day ..in fact over a few days..so wrote a program to calculate spoke length.

Yes a spreadsheet or an online calculator is probably quicker, but at least with this calc you know exactly what you are getting..I find many on-lien calculators all give fractionally different results.


If you enter Zero when running the program, it keeps the previously entered value , apart from the Cross figure as Zero is needed for radial patterns

Can use Cross figure up to 4, or spoke angle and rim angular spacing if doing 'weird' patterns like 36 hole hub to 24 hole rims etc where there you have non regular cross numbers, and multiple spoke lengths etc.


you have to punch it in manually

but here it is if any use


"Spoke length"
"ERD"?→Z:Z>0 Z÷2→R
"RIM HOLE OFFSET"? →Q
"LH HUB DIA"? →Z:Z>0⇒Z÷2→D
"RH HUB DIA"? →Z:Z>0⇒Z÷2→G
"L FLNGE – CNT"? →Z:Z>0⇒Z-Q→I
"R FLNGE – CNT"? →Z:Z>0⇒Z-Q→J
"SPOKE HOLE DIA"? →Z:Z>0⇒Z÷2→O
"CROSS OR ANGLE"? →Z:Z>4⇒Goto1:Goto2

Lbl 1:Z→A:"RIM HOLE ANGULAR SPACING"? →Z:Z>0⇒Z→B:A÷2B→X:"CROSS=":X◄
Goto3
Lbl 2:Z→X:"NUMBER OF RIM HOLES"? →Z:Z>0⇒Z→H((720÷H)xX) →A:"SPOKEANGLE="A◄
Lbl 3
((√(R2+D2+ I2-(2RDcos A)))-O)→M
((√(R2+G2+ J2-(2RGcos A)))-O)→N
"LEFT LENGTH=":M◄
"RIGHT LENGTH=":N◄

 

[OldBlokOldBikes]

I wish I still had my graphic calculator!

 

[Skyfarmer]

plenty on flea bay

http://www.ebay.co.uk/itm/Casio-fx-7700 ... 19eca8c290

http://www.ebay.co.uk/itm/Casio-fx-7700 ... 3a8fc963f1

 

[OldBlokOldBikes]

Don't get me started on retro-calcualtors as well!

(I had a fx-7000G - that makes me old)

http://en.wikipedia.org/wiki/Casio_fx-7000G

 

[Skyfarmer]

Yes, had one too...but it possible died...I will have to dig it out....ummm...a new sub forum

 

[FluffyChicken]

Re:

The differences in the calculators are down to preference of where they want the spoke end to stop, person fudge factors found to work. And often if the use spoke hole diameter or not. Very few even bother with slight offsets like you have on m231 rims.

A few tenths of a mm here or there is nothing to worry about.

Still I'm sure I might have to get my 7700 out and pksy some retro projectile games on it.

 

[FMJ]

"Spoke length"
"ERD"?→Z:Z>0 Z÷2→R
"RIM HOLE OFFSET"? →Q
"LH HUB DIA"? →Z:Z>0⇒Z÷2→D
"RH HUB DIA"? →Z:Z>0⇒Z÷2→G
"L FLNGE – CNT"? →Z:Z>0⇒Z-Q→I
"R FLNGE – CNT"? →Z:Z>0⇒Z-Q→J
"SPOKE HOLE DIA"? →Z:Z>0⇒Z÷2→O
"CROSS OR ANGLE"? →Z:Z>4⇒Goto1:Goto2

Lbl 1:Z→A:"RIM HOLE ANGULAR SPACING"? →Z:Z>0⇒Z→B:A÷2B→X:"CROSS=":X◄
Goto3
Lbl 2:Z→X:"NUMBER OF RIM HOLES"? →Z:Z>0⇒Z→H((720÷H)xX) →A:"SPOKEANGLE="A◄
Lbl 3
((√(R2+D2+ I2-(2RDcos A)))-O)→M
((√(R2+G2+ J2-(2RGcos A)))-O)→N
"LEFT LENGTH=":M◄
"RIGHT LENGTH=":N◄

Uh......Greek?

This works pretty good.

 

[latman]

maybe you can tell me if the spokes in this NOS front wheel I bought (mavic GL330 and Deore XT hub) will be usable for the mavic 550 rear hub I am going to rebuild it with ? i think the spoke hole diameter of the XT is 38mm and the 550 is 43mm

 

[latman]

i was just going to wing it and see if it worked ?, I am sure the NDS would be ok but concerned the DS spokes will be too long despite being able to see a few spoke threads in the rim photo..

 

[Skyfarmer]

Fluffy,
Yes, Differences between online calcs in real world are irrelevant, but that was not good enough for me. But if you enter the same figures I'd at least expect same answer. I am not sure how they come up with different answers. The trig should be the same, therefore formulas used should be the same. Some ignore spoke hole diameter, so when using thicker gauge spokes it puts the calc out again .

My main problem with some of them is the inability to use fractional cross numbers or spoke angles for ' weird ' wheel builds, like a kids ' kick scooter' I did a while back. 36 hole hub, and 24 or 28 hole rim. 5 different spoke lengths, from a radial spoke to the longest at about 2.6 cross.
Only one on line calc does decimal fraction crosses, but I prefer spoke angle, which no online calcs use.

→A:"SPOKEANGLE="A◄
Lbl 3
((√(R2+D2+ I2-(2RDcos A)))-O)→M
((√(R2+G2+ J2-(2RGcos A)))-O)→N
"LEFT LENGTH=":M◄
"RIGHT LENGTH=":N◄

Uh......Greek?

This works pretty good.

Yes, pretty much like Greek if you are not into programming. But actually quite readable.
I did search for iPad/iPhone apps, but none allow for decimal crosses or spoke angles, or spoke bed offsets..Waht is the pic of the one you took screen grab from? can't find it by that name on the iPad app store

As for using the spokes again on the rear hub.ummm well 6 mm diameter difference, so radius is half that...
If rear hub flanges are wider too, that may take some slack up.

Double walled rim? Not looked it up, but if so you could get away with spokes extending past nipple a bit, if there is enough threaded section.

Measure the widths too, from locknut on axle to flange centre, on both sides, both hubs. And axle widths.... Assuming 110ish front and 135 rear?